JH, I spent my spotting days at EGNX in the early 70's listening to 'PNE, 'PND, 'SED and 'VJB make exactly the sound you describe. AND we spotted the Pink Floyd thing within a week of "Dark Side" being released!
It's thread drift I know, but some other "sounds of the '70s" also need explaining:-
1 The BAC 1-11 startup rising whine and sudden cutoff, and the spooky howling noise at about 2-4000ft and 250-170kts in the descent. Heard this around midnight near Loughborough (April 1970ish), and in the still of the night it scared the hell out of me until I realised it was new Midland 1-11 coming home!
2 The characteristic bleep at the end of a Tx from a 1-11 500srs radio.
('XLL, 'XLM, 'XLN and of course the BEA GAVM* models for example).
However, none of these audiable delights compete with the 'music' that is geneated by XV105 and her 53 beautiful sisters.
